The present invention relates to an apparatus, a processing method and a wafer probe for processing a semiconductor wafer using plasma.
Due to high integration of a semiconductor device in recent years, the circuit pattern goes on becoming fine, and the required processing size accuracy has been more and more severe. Furthermore, for the purpose of improving the productivity, besides the enlarging of the diameter of the wafer size is progressing, in order to improve the performance of the devices, the application of new materials and the change of wiring structure are considered. Furthermore, together with this, the development of new processing technique is in progress, and the development of the processing technique is very difficult and costly.
Moreover, in the apparatus of performing the processing of wafers using plasma, among the semiconductor manufacturing apparatuses, for example, in plasma etchers and plasma CVDs, it is very important to accurately grasp and control the energy of ions incident on the substrate, and this leads to the reduction of the start-up period of the process. Conversely, when the ion energy is not accurately grasped, a problem arises in which variations of the performance of the products are caused, and the yield is also decreased.
An example of the method of monitoring and controlling the energy of ions incident on a substrate under plasma processing is disclosed, for example in JP-A-7-135180. In this disclosed example, a method of measuring the voltage of a substrate under processing is disclosed in which the electrode mounting thereon the substrate to be processed is grounded through a condenser, and voltage measuring means for measuring the voltage between the condenser and the electrode is provided.
Furthermore, in U.S. Pat. No. 5,808,415 and U.S. Pat. No. 6,061,006, there are disclosed respectively a manufacturing method of a probe for measuring a current and a voltage applied to plasma, and a manner of obtaining a plasma impedance within a plasma chamber.
However, in the example disclosed in JP-A-7-135180, as a method of measuring a surface voltage of a substrate in order to control the energy of ions incident on the substrate, a voltage between the electrode mounting thereon the substrate and a condenser connected to this electrode is measured by a voltmeter, and a problem may arise because the voltage of the substrate is not directly measured. For example, in the case of etching processing by fixing the substrate by absorbing by an electrostatic chuck, there is an example, in which as the number of processed wafers is increased, deposition will be attached to the surface of the electrostatic chuck. This will be explained with reference to FIG. 10. In the disclosed example, in order to obtain a surface voltage Vg, a condenser C1 whose capacitance is known is connected to an electrode which mounts thereon a substrate. And the capacitance Cg of the substrate is investigated beforehand, and the voltage Vs is measured by the means shown in the disclosed example, and the surface voltage Vg is obtained by calculating Vs+(C1/Cg) * Vs. In the case where the electrode has the function of the electrostatic chuck, and where a dielectric film or the like is attached to the electrode surface, Cg may be corrected taking the capacitance of the dielectric film into consideration. If the deposition is attached to the surface of the dielectric film just after the start of the etching processing, since the capacitance Cg will be changed, eventually it will not be able to obtain the voltage of the substrate accurately.
Furthermore, in the actual manufacturing apparatus, not only the terminal connected to the electrode is electrically connected to the substrate through the electrode but also there exist an electric circuit connected to earth through a condenser component, and an inductance component of a power supply line for supplying high frequency power. Accordingly, even if a voltage across the condenser connected to the electrode is simply measured, it is not said that the voltage of the substrate is accurately measured.
Also, for example, in the etching processing or the like, when a reaction product or the like has been attached to an inner wall of a vacuum chamber enclosing a plasma, even if the voltage of the substrate could be measured by the method of the disclosed example, in the case where the state of the plasma itself has been changed, there is a possibility that the processed result will be changed even if the voltage of the substrate is controlled.
On the other hand, in the disclosed examples of U.S. Pat. No. 5,808,415 and U.S. Pat. No. 6,061,006, a method of obtaining a real plasma impedance from a current and a voltage waveform exsisting within the discharge is disclosed in which an impedance network of the plasma chamber is expressed by a chamber resistance, an electrode inductance, a stray capacitance between an electrode and ground, and a stray capacitance. However, in the disclosed examples, since the surface voltage of the wafer under processing in the plasma cannot be obtained, there is a problem that the ion energy incident on the wafer cannot be controlled.
In order to solve these problems, it is necessary that both the voltage of the substrate and the plasma impedance are measured or obtained by calculation, and depending on the case, the impedance of the deposition attached to the inner wall of the vacuum chamber is measured or obtained by calculation, and it is necessary to appropriately control the etching parameters based on these information.
Therefore, a first object of the present invention is, in the semiconductor manufacturing apparatus using a plasma, to provide a semiconductor manufacturing apparatus and a processing method in which a voltage of a substrate under processing and an impedance between the substrate and earth through the plasma are measured or obtained by calculation.
A second object of the present invention is, in the semiconductor manufacturing apparatus using a plasma, to provide a semiconductor manufacturing apparatus and a processing method in which a voltage of a substrate under processing and an impedance between the substrate and earth through the plasma are measured or obtained by calculation, and an etching parameter is controlled on the basis of these information.
A third object of the present invention is, in the semiconductor manufacturing apparatus using a plasma, to provide a semiconductor manufacturing apparatus and a processing method in which an appropriate cleaning time can be easily determined by monitoring a thickness of a film deposited on an inner wall of a vacuum chamber.
A fourth object of the present invention is, in the semiconductor manufacturing apparatus using a plasma, to provide a semiconductor manufacturing apparatus and a processing method in which a voltage of a substrate under processing, a voltage of a susceptor disposed to surround the substrate, an impedance to earth through the plasma above the substrate under processing, and an impedance to earth through the plasma above the susceptor are measured or obtained by calculation, and based on theses information, the bias voltage applied to the substrate and the susceptor can be controlled independently.
A fifth object of the present invention is to provide a probe capable of measuring a voltage of the substrate under processing and of the susceptor disposed to surround the substrate.
The first object mentioned above can be achieved, for example, in the semiconductor manufacturing apparatus for precessing a semiconductor wafer using a plasma, by providing a wafer voltage probe for measuring a voltage of the semiconductor wafer from a rear surface of the semiconductor wafer, and a current and voltage probe for measuring at least one of a voltage value and a current value applied to a wafer stage from a high frequency power supply, and by calculating an impedance to earth through the plasma above the semiconductor wafer based on the voltage value of the semiconductor wafer measured by the wafer voltage probe, and the voltage value or the current value measured by the current and voltage probe.
Furthermore, the second object can be achieved, for example, by controlling various processing parameters on the basis of at least one of the obtained impedance and the wafer voltage.
Also, it is possible to achieve, for example, by calculating an impedance based on a voltage and a current measured by the current and voltage probe, and then performing an arithmetic processing of a combined impedance of the impedance calculated above and an equivalent circuit model extending from a high frequency power supply (accurately, the current and voltage probe) to earth through a plasma, which equivalent circuit model being obtained beforehand, thereby to calculate an impedance from the wafer to earth through the plasma and a voltage of the wafer, and by controlling various parameters based on the last mentioned impedance and the voltage of the wafer.
Also, for example, a film thickness probe capable of measuring a film thickness of a film deposited on the inner wall of the vacuum chamber is provided, and if an impedance of the film thickness measured by this probe is calculated, since the impedance (plasma impedance) between the wafer and the surface of the film attached to the inner wall of the vacuum chamber can be accurately calculated, it is only necessary to control various parameters based on this information and it becomes possible to control the etching with sufficient precision.
The third object mentioned above can be achieved, for example, in the semiconductor manufacturing apparatus for processing a semiconductor wafer using a plasma, by providing means capable of measuring a film thickness of the film deposited on the inner wall of the vacuum chamber, and by monitoring the film thickness during processing.
The fourth object mentioned above can be achieved, for example, in the semiconductor manufacturing apparatus for processing a semiconductor wafer using a plasma, by providing a wafer voltage probe for measuring a voltage of the semiconductor wafer from a rear surface of the semiconductor wafer, a current and voltage probe for measuring at least one of a voltage value and a current value applied to a wafer stage from a high frequency power supply, and a susceptor voltage probe for measuring a voltage of a susceptor disposed to surround the semiconductor wafer, and by calculating an impedance to earth through the plasma above the semiconductor wafer and an impedance to earth through the plasma above the susceptor, on the basis of the voltage value of the semiconductor wafer measured by the wafer voltage probe, and the voltage value or the current value measured by the current and voltage probe, and the voltage value of the susceptor measured by the susceptor voltage probe, and by controlling the high frequency voltage applied to the semiconductor wafer and to the susceptor independently.
Also, for example, if a film thickness probe capable of measuring a film thickness of a film deposited on the inner wall of the vacuum chamber is provided, and if the impedance of the film thickness measured by this probe is calculated, since it is possible to calculate the impedance from the wafer to the surface of the film deposited on the inner wall of the vacuum chamber and the impedance from the susceptor to the surface of the film deposited on the inner wall of the vacuum chamber, if various parameters are controlled based on this information, it will become possible to control the etching with sufficient precision.
The fifth object mentioned above can be achieved, for example, by supporting with a resilient member having electrical conductivity, a contact needle having electrical conductivity to make contact with the rear surface of the semiconductor wafer whose voltage is to be measured, and by exposing the resilient member to atmospheric side in a condition electrically insulated from a flange for securing the resilient member to the vacuum chamber, and by measuring the voltage at this portion.
Also, for example, it becomes possible to measure with reproducibility by making adjustable the position of the contact needle in the height direction. Furthermore, if the material of the contact needle is made harder than a hardness of silicon oxide exsisting on the rear surface of the wafer, it will become possible to measure with further reproducibility.